Metal injection molding (MIM) is a metalworking process useful in creating a variety of metal objects. A mixture of powdered metal and binder (e.g., a polymer such as polypropylene) forms a “feedstock” capable of being molded, at a high temperature, into the shape of a desired object. The initial molded part, also referred to as a “green part,” then undergoes a debinding process to remove the binder, followed by a sintering process. During sintering, the part is brought to a temperature near the melting point of the powdered metal, which evaporates any remaining binder and forming the metal powder into a solid mass, thereby producing the desired object.
Additive manufacturing, also referred to as 3D printing, includes a variety of techniques for manufacturing a three-dimensional object via an automated process of forming successive layers of the object. 3D printers may utilize a feedstock comparable to that used in MIM, thereby creating a green part without the need for a mold. The green part may then undergo comparable debinding and sintering processes to produce the object.
Furnaces used for debinding and sintering of green objects and brown objects typically employ conventional thermal heating methods or direct microwave sintering. Microwave thermal processing has been performed at extremely high temperatures (e.g., 500-900 C and above) in the context of ceramic processing, and much less commonly in the context of metal sintering. In general, microwave-enhanced processing can provide external heating to a part by way of conventional heating elements while simultaneously providing some degree of internal heating by way of microwaves.